Allergic asthma, mediated by pathologic Th2-type immune responses, is a major healthy problem in western countries. Symptoms of allergic asthma include increased mucus production and airway hyper-responsiveness. Repetitive exposure to allergens is an important contributing factor to this disease.
Steroids and other anti-inflammatory drugs are commonly used for treating allergic asthma. These drugs only alleviate asthma syndromes and do not prevent occurrence of allergic immune responses. Recently, allergy vaccine was developed as a preventive approach. A typical allergy vaccine contains an allergen (e.g., a pollen allergen or a microbial allergen) to induce specific immune responses and an adjuvant (e.g., CpG oligonucleotide or a mutated E. coli heat-labile enterotoxin) to enhance the allergen-specific immune responses.